Add completions for closing tag name

[mhegazy]

TypeScript Version: 3.0.0-dev.201xxxxx

Search Terms:

Code

var x = <Comp> <|  // Completion here

Expected behavior:

The list should contain /Comp>.

Actual behavior:

No completion list

Playground Link:

Related Issues: #20811

Don't think this is necessary now that we have #24543; we also already have a completion after / is typed, so this would only save a single character, that you would probably have to type anyway to select the completion out of the list.